1. Field of the Invention
The present invention relates to a packaging article and a corresponding manufacturing method and apparatus.
2. Description of the Prior Art
Modified-atmosphere packaging (MAP) or controlled-atmosphere packaging (CAP) are terms used to describe packaging systems designed to impede or deter food aging processes and extend the shelf-life of fresh food. Central to these packaging systems is the principle of surrounding the food product with a gaseous environment formulated to slow the natural processes of oxidation, respiration and ripening. Typical constituents of such an environment include oxygen, nitrogen, carbon dioxide, ethylene and water vapor. This gaseous environment is confined about the food product by a barrier material package having designed permeability characteristics respective to those gases which are to be maintained within the confinement volume and/or those to be excluded from it.
Prior art packages for MAP and CAP applications are constructed entirely of plastic; typically consisting of a 20-50 mil thick, generally multi-layered, thermoformed tray covered by a heat-sealed lid of plastic film. Both barrier and structural properties are provided by the polymer materials. Packaging graphics are provided by independently applied paper labels or a separate paperboard carton.
Insofar as a gaseous barrier is required of such a package, a 3-5 mil (prethermoformed) sheet thickness of polymer is sufficient; the remaining mass of prior art plastic package thickness being devoted to the structural function. However, the same structural function is readily accomplished by a 7-35 mil thickness of paperboard which is not only substantially less expensive than plastic but is also biodegradable. Moreover, content identification and promotional graphics may be applied to paperboard prior to cutting and forming the container blank.
On the other hand, paperboard is a stiff, essentially planar material having limited yield and stretch capacity to be formed to the warped surfaces of vessels, trays and other containers. In less demanding packaging systems, such containers are formed by folded lap joints secured by adhesives. However, such joints are frequently discontinuous and tend to leak fluids.
Although it is known that others have attempted to fabricate MAP and CAP systems by vacuum drawing continuous polymer film into the interior of a pre-erected paperboard vessel, success with such systems has been limited. Non-uniformity of vacuum distribution prevents full corner contact of the film into the vessel interior. Additionally, vacuum formed barriers are plagued with pin-holing and poor barrier adhesion.
Considerable fabrication and marketing success has been achieved with paperboard vessels lined with thermoformed polystryene or polyvinyl chloride film. However, these polymers have severe limitations in a microwave oven environment.
It is, therefore, an object of the present invention to teach a method and apparatus for applying a continuous, thin but adequate gas barrier of blow molded polymer film such as polypropylene base materials to the interior of a fold formed paperboard vessel shape which could be microwaved with most food products.
Another object of the present invention is to provide the food processing and distribution industry with a high quality MAP/CAP system at substantially less cost than most solid polymer vessel systems that are presently available.
Another object of the present invention is to provide the food processing and distribution industry with a gas tight package article that may be printed with high quality graphics prior to forming and filling.
Another object of the present invention is to provide the food processing and distribution industry with a microwaveable paperboard asceptic packaging unit.